Combine all themes into a single playground (rjsf-team#1539)

* move playground to new folder

* move playground to packages and standardize playground structure

* don't rely on bootstrap in playground

* fix styling, move share button to top right

* remove footer things

* more fixes

* encode theme in playground hash

* fix: don't switch to default theme when changing tabs

* correct package name is @rjsf/playground

* fix prod config for playground

* fix more configs

* use webpack-dev-server

* render form in a Frame

* add dependencies

* use DemoFrame component to properly fix material-ui styles

* use old bootstrap look and feel for the playground itself

* fix dist

* move netlify toml

* update netlify

* empty commit

* remove npm prepare to speed up travis runs

* fix webpack dist config for playground

* fix import

* disable minicssextractplugin to try to fix netlify

* fix netlify path

* no need to build playground / gh-pages for core package

* add HtmlWebpackPlugin

Author: epicfaace

netlify.toml

@@ -0,0 +1,7 @@
+[build]
+  base = "packages/playground"
+  publish = "build"
+  command = "npm run build:playground"
+
+[build.environment]
+  SHOW_NETLIFY_BADGE = "true"

packages/core/package.json

@@ -5,14 +5,11 @@
   "scripts": {
     "build:lib": "rimraf lib && cross-env NODE_ENV=production babel -d lib/ src/",
     "build:dist": "rimraf dist && cross-env NODE_ENV=production webpack --config webpack.config.dist.js",
-    "build:playground": "rimraf build && cross-env NODE_ENV=production webpack --config webpack.config.prod.js && cp playground/index.prod.html build/index.html",
     "cs-check": "prettier -l \"{playground,src,test}/**/*.js\"",
     "cs-format": "prettier \"{playground,src,test}/**/*.js\" --write",
     "dist": "npm run build:lib && npm run build:dist",
     "lint": "eslint src test playground",
-    "prepare": "npm run dist",
     "precommit": "lint-staged",
-    "publish-to-gh-pages": "npm run build:playground && gh-pages --dist build/",
     "publish-to-npm": "npm run dist && npm publish",
     "preversion": "npm run build:playground && npm run dist && npm run cs-check && npm run lint",
     "start": "node devServer.js",